- Figures l, Figure 4. 2, and 3. 26 Longitudinal sections through the heads of silver salmon spermatozoa. Sections of spermatozoan tails showing a longi- tudinal section (A), oblique sections (B), and a cross section (C). Substructure within the fibrils is shown in the oblique sections. Figures 5 and 6. Cross sections through spermatozoan tails showing the spindle-shaped sheath and multiple unit fibrils. mg - mitochondrial granule cs - cytoplasmic sheath ns - nuclear sheath - nuclear material pe - - proximal centriole dc distal centriole rf - ring fibril cf - central fibril np ~ neckpiece gr - golgi remnant